SE7501646L - - Google Patents

Abstract

1489442 Sonar apparatus WESTINGHOUSE ELECTRIC CORP 11 Feb 1975 [21 Feb 1974] 5720/75 Heading G1G The output signals of a receiver transducer array in a side-scan sonar are electronically processed to provide a receiver focus which varies in range following each acoustic transmission. In the embodiments described the sonar is towed, submerged, and the receiver beam is fanshaped and directed to port and/or starboard. Fig. 8 shows a receiver array 56 with time-varied gain applied at 58-1 to 58-9 to its signals. Mixers 60-1 to 60-9 combine the array signals (of frequency fs) with local oscillator signals (of frequency fm) which have been given various phaseshifts in a shift-register 65 clocked at a rate fc. The phase-shifts are such that the array is focused at a given range. By linearly sweeping the frequency fc this range is varied with time so that all points on a seabed target strip are in focus. The mixer outputs are summed at 85, the difference frequency fs-fm being extracted at 87 and detected at 89 for driving display 90. By more elaborate processing of the array signals several adjacent parallel receiver beams can be formed simultaneously, Fig. 16, (not shown), thus permitting a faster scan of the target area. Further phase-shifting of the local oscillator signals enables the receiver beam(s) to be rotated in azimuth to compensate automatically for yawing motion of the sonar, Fig. 17 (not shown). When port and starboard receiver arrays are used, for reception of frequencies fs,fs' respectively, both frequencies are processed by common mixer channels and resulting difference frequencies fs-fm and fs'-fm are extracted by respective filters for detection and display Fig. 19 (not shown). Amplitudeshading of the array signals, for side-lobe suppression, is mentioned.